Electric resistivity survey is a survey method that is prompt and effective in identifying a fault, a fracture zone, a rock border, and the like.
Electrode arrays mainly used in electric resistivity survey most widely used in groundwater exploration include a pole-pole array, a pole-dipole array, and a dipole-dipole array. However, a modified pole-pole array and a dipole-dipole array, in which a negative potential electrode and a current electrode are secured to opposite ends of a survey line due to difficulty in connection to ground according to field conditions, are currently most commonly employed.
FIG. 1a is a conceptual diagram of arrangement of electrodes in a dipole-dipole array, and FIG. 2b is a conceptual diagram of arrangement of electrodes in a modified pole-pole array.
In order to survey underground water and identify a geological structure, a fault and a fracture zone of a subsurface of less than 50 m under the ground, a high-resolution electric resistivity survey is performed with electrodes separated a distance of 5 m, 10 m or less from each other. To this end, more than 100 potential and current electrodes are disposed along a survey line. In this case, to connect an electric wire to an electrode, a banana jack is connected to the electric wire and is inserted into the electrode having a hole, or an electric wire is connected by an electrical tape as shown in FIG. 2.
However, since the method of connecting a banana jack to an electric wire consumes considerable time and cost and contact errors frequently occur in proportion to the number of times of use, measurement data can have an error and considerable time is consumed to correct the error.
Further, when an electric wire is provided to an electrode using electrical tape as shown in FIG. 2, a large amount of the electrical tape is necessary and considerable time is required to install and withdraw the electrode.
In addition, if the electric wire is erroneously pulled or touched in the course of connecting the electric wire to the electrode using the electrical tape, the electric wire can be separated from the electrode, thereby causing an error in measurement data. In particular, in rainy weather or in a season when it is humid in the morning and in the evening, a contact error can occur due to moisture and the electrical tape can be frozen in winter, thereby causing frequent separation of the electrode.
Further, when the electrode is withdrawn after the survey, the electrical tape needs to be manually released and considerable time is required to separate the electrode from the wire. Moreover, the separated electrical tape cannot be reused and is generally discarded on the ground, causing environmental contamination.